opera has come a long way for sure, and follow the standards. FF is good about following them, too. There's nothing wrong with these browsers.
Just had to upgrade a TinyMCE installation in a CMS once the IE 10 bomb dropped lol It had worked in 7 & up, Chrome, FireFox, Opera, Safari and I even tried it in IE 6 on a old server still running 2000 server, worked fine. I didn't bother to find the actual problem since the JS was minimized, but I suspect I have more coming my way soon. That's my beef with IE. They've always follow the beat of their own drum and make cross browser development that's consistent a real head ache. Then they upgrade and stuff that has worked for years is now suddenly broken (reminds me of Win8). IE makes me face palm, but it's a transparent problem to people that don't have to deal that aspect.
Don't get me started on debugging in IE either, that's just as big of headache. I got tasked one time of finding out why some third party CSS3 emulation scripts were causing IE 9 to completely bomb out. It was something stupid in the style sheet to boot. I will test and support IE, but it's not the browser I use.